The growth of solid tumors is strictly dependent on new blood vessel formation. This relationship has stimulated efforts to identify new gene products and drugs which regulate blood vessel growth in tumors, a process referred to as tumor angiogenesis. However, progress has been hindered by major gaps in our understanding of this process. We performed confocal imaging and 3D reconstruction of a series of breast cancers isolated from transgenic mice bearing different initiating mutations. We observed very significant variations in vascular pattern and expression of angiogenic mediators that were transgene specific. In this proposal. we present experiments to dissect the angiogenic response of tumors which overexpress TGF-beta1. TGF-beta family members are found at significant levels in as many a 80% of epithelial tumors, and in a large percentage of advanced breast cancers. We have developed a line of genetically defined mice which allow the analysis of the effects of TGF- beta1 on growth and vascularization of breast tumors. The system relies on expression of a dominant oncogene, wnt10b. We observe that tumors expressing wnt10b and TGF-beta1 are significantly more vascularized and metastasize more readily than wnt10b overexpressing tumors alone. Using this system. we propose to study various angiogenic parameters. elucidate cellular and molecular targets of TGFbeta1 induced angiogenesis, and finally to assess the response of these tumors to three classes of antiangiogenic therapy. In particular. we propose to characterize tumors induced by transgenic overexpression of wnt10b alone, or in combination with TGF-beta1, for expression of angiogenic stimulators and inhibitors, and correlate this profile with vascular density, vessel size, and number (Aim l). We have reestablished the system in non-transformed Eph4 cells and propose to analyze the ability of blocking antibodies, and dominant negative TGFbeta-RcII cDNA's to suppress angiogenic activity of conditioned medium. We will create mice that lack TGFbeta-RcII expression in adult endothelial cells test the response to tumor derived stimulation (Aim 2). Finally, we will treat tumors three class of anti- angiogenic therapy, including: (a) soluble fit; (b) TSP1-derived peptides; or (c) METH-l, to assess their effects on TGF-beta1 induced tumor angiogenesis (Aim 3). We feel that this broad based approach will help to establish the relationship between TGF-beta1 overexpression and tumor angiogenesis, improve our understanding of genes involved in tumor responsive endothelial growth, and dissect the pathway of TGF-beta1 induced angiogenesis through an analysis of specific inhibitors.